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United States Patent |
5,585,147
|
Ogawa
,   et al.
|
December 17, 1996
|
Process for a surface treatment of a glass fabric
Abstract
A surface treatment of a glass fabric used for a fiber reinforced composite
such as multilayer circuit boards comprises the steps of exposing the
glass fabric to an atmospheric pressure plasma of a mixture gas to obtain
a plasma-treated surface of the glass fabric, and coating an organosilane
compound on the plasma-treated surface. The mixture gas contains as a
reaction gas at least one of an oxidative gas and a fluorine-containing
gas, and a rare gas as a carrier of the reaction gas. The mixture gas is
pre-heated prior to the plasma excitation thereof. When the glass fabric
includes an organic compound as a sizing agent, the organic compound can
be efficiently removed from the glass fabric by the exposing step. For
example, the organosilane compound can be coated on the plasma-treated
surface by exposing the plasma-treated surface to a second atmospheric
pressure plasma of a second mixture gas containing an organosilane
monomer. The surface treatment of the present invention is useful to
efficiently produce a multilayer circuit board having excellent adhesion
between the glass fabric and a resin, and resistance to CAF (Conductive
Anodic Filaments).
Inventors:
|
Ogawa; Satoru (Hirakata, JP);
Sawada; Yasushi (Neyagawa, JP);
Matsumura; Masahiro (Katano, JP);
Nakamura; Yoshihiko (Nishinomiya, JP)
|
Assignee:
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Matsushita Electric Works, Ltd. (Osaka, JP)
|
Appl. No.:
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446476 |
Filed:
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May 22, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
427/535; 427/255.24; 427/299; 427/561; 427/570; 427/574; 427/578 |
Intern'l Class: |
H05H 001/00 |
Field of Search: |
427/534,535,569,570,307,255.3,299,561,574,578
|
References Cited
U.S. Patent Documents
5124173 | Jun., 1992 | Uchiyama et al. | 427/38.
|
5275665 | Jan., 1994 | Okazaki et al. | 118/723.
|
Foreign Patent Documents |
62-111493 | May., 1987 | JP.
| |
641733 | Jan., 1989 | JP.
| |
641734 | Jan., 1989 | JP.
| |
641735 | Jan., 1989 | JP.
| |
Primary Examiner: Pianalto; Bernard
Attorney, Agent or Firm: Watson Cole Stevens Davis, P.L.L.C.
Claims
What is claimed is:
1. A process for a surface treatment of a glass fabric, said process
comprising the steps of:
exposing a glass fabric to an atmospheric pressure plasma of a mixture gas
including a reaction gas to obtain a plasma-treated surface of said glass
fabric, said mixture gas being pre-heated to a temperature between
100.degree. C. to 500.degree. C. prior to a plasma excitation thereof; and
coating an organosilane compound on the plasma-treated surface of said
glass fabric.
2. A process as set forth in claim 1, wherein said organosilane compound is
coated on said plasma-treated surface by exposing said plasma-treated
surface to a second atmospheric pressure plasma of a second mixture gas
containing a vaporized gas of an organosilane monomer.
3. A process as set forth in claim 2, wherein said second mixture gas is
heated at a temperature of 100.degree. C. to 500.degree. C. prior to a
plasma excitation thereof.
4. A process as set forth in claim 1, wherein a heat-cleaning treatment is
performed to said glass fabric prior to said exposing step.
5. A process for a surface treatment of a glass fabric including an organic
compound, said process comprising the steps of:
removing organic compound from a glass fabric in an atmospheric pressure
plasma of a mixture gas to obtain a plasma-treated surface of said glass
fabric, said mixture gas containing as a reaction gas at least one of an
oxidative gas and a fluorine-containing gas, and a rare gas as a carrier
of said reaction gas, said mixture gas being pre-heated to a temperature
between 50.degree. C. and 600.degree. C. prior to a plasma excitation
thereof; and
coating an organosilane compound on the plasma-treated surface of said
glass fabric.
6. A process for a surface treatment of a glass fabric, said process
comprising the steps of:
exposing a glass fabric to an atmospheric pressure plasma of a mixture gas
including a reaction gas to obtain a plasma-treated surface of said glass
fabric, said mixture gas being pre-heated to a temperature between
50.degree. C. to 600.degree. C. prior to a plasma excitation thereof; and
coating an organosilane compound on the plasma-treated surface of said
glass fabric.
7. A process as set forth in claim 6, wherein said reaction gas is at least
one of an oxidative gas and a fluorine-containing gas.
8. A process as set forth in claim 7, wherein said oxidative gas is at
least one gas selected from the group consisting of oxygen, air, and
carbon dioxide.
9. A process as set forth in claim 7, wherein said fluorine-containing gas
is at least one gas selected from the group consisting of hydrofluoride
(HF), sulfur hexafluoride (SF.sub.6), fluorine, nitrogen trifiuoride
(NF.sub.3), carbon tetrafluoride (CF.sub.4), trifiuoromethane (CHF.sub.3),
and dicarbon hexafluoride (C.sub.2 F.sub.6).
10. A process as set forth in claim 6, wherein said exposing step comprises
the sub-steps of:
exposing said glass fabric to a first atmospheric pressure plasma of a
first reaction gas containing an oxidative gas to obtain a pre-treated
surface of said glass fabric; and
exposing said pre-treated surface to a second atmospheric pressure plasma
of a second reaction gas containing a fluorine-containing gas to obtain
said plasma-treated surface of said glass fabric.
11. A process as set forth in claim 6, wherein said reaction gas is one of
a hydrogen-containing gas and a mixture of hydrogen gas and a
fluorine-containing gas.
12. A process as set forth in claim 6, wherein said organosilane compound
is coated on said plasma-treated surface of said glass fabric by
impregnating a solution containing said organosilane compound into said
glass fabric, and drying said solution in said glass fabric.
13. A process as set forth in claim 6, wherein said plasma is excited by
using an alternating current power source of a frequency of 50 Hz to 13.
14. A process for a surface treatment of a glass fabric, said process
comprising the steps of:
exposing a glass fabric to an atmospheric pressure plasma of a mixture gas
including a reaction gas to obtain a plasma-treated surface of said glass
fabric, said mixture gas being pre-heated to a temperature between
100.degree. C. to 600.degree. C. prior to a plasma excitation thereof; and
coating an organosilane compound on the plasma-treated surface of said
glass fabric.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates a surface treatment of a glass fabric used
for a fiber reinforced composite such as multilayer circuit boards.
2. Disclosure of the Prior Art
In the past, glass yarns coated with an organic compound are woven to
obtain a glass fabric used to make a fiber reinforced composite such
multilayer circuit boards. The organic compound is called as a sizing
agent and acts as a protecting film for the glass yarns. After a weaving
step the glass fabric is heated at about 400.degree. C. over a period of
several tens of hours to remove the organic compound from the glass
fabric. This heat treatment is known as a heat-cleaning treatment.
Subsequently the glass fabric, free of the organic compound, is treated
with a coupling agent to improve adhesion between the glass fabric and a
resin which is used at a later stage of manufacturing the multilayer
circuits boards. An organosilane compound can be used as the coupling
agent. For example, the glass fabric may be dipped in a solution including
the coupling agent diluted with an organic solvent or water. The resin is
impregnated into the treated glass fabric to a form a prepreg. The
multilayer circuit board can be manufactured by stacking and compressing a
plurality of copper foils and prepregs.
When the organic compound is not sufficiently removed from the glass fabric
by the heat-cleaning treatment, there arises a problem of decreasing the
adhesion between the glass fabric and the resin because the glass fabric
can not be uniformly,treated with the coupling agent. In addition, when
carbon is left on the glass fabric as a residue of the organic compound,
there is a probability of adversely influencing the insulating property of
the fiber reinforced composite.
Thus, the heat-cleaning treatment is an important step necessary for
producing good multilayer circuit boards. However, as described above,
since the heat-cleaning treatment requires heating the glass fabric at
about 400.degree. C. over the period of several tens of hours, there is a
problem of providing a low production rate of the glass fabric, free of
the organic compound, in spite of using a relatively large amount of
energy. To improve the production rate, Japanese Patent Early Publications
[KOKAI] Nos. 62-111493 and 64-1733 to 1735 propose to perform a plasma
treatment to the glass fabric under a reduced pressure to remove the
organic compound from the glass fabric, or perform the plasma treatment
simultaneously with the heat-cleaning treatment. However, since the plasma
treatment is performed under a reduced pressure, there is a problem of
requiring an expensive and complex furnace with a vacuum apparatus.
On the other hand, for small-sizing electronic devices and providing high
performance to the devices, it is desired to produce printed circuit
boards or multilayer printed boards having high-density circuits. In
particular, as a distance between through-holes or a distance between a
conductive pattern of an internal layer of the multilayer printed board
and a through-hole becomes to be shorter to form the high-density
circuits, there arises an undesired phenomenon of deteriorating the
insulating property therebetween. As one of the reasons for such a
phenomenon, the influence of copper migration should be considered. The
copper migration is explained as follows. That is, when an electric
potential is applied between copper circuits under the condition of high
humidity, copper of the circuit corresponding to an anode is dissolved,
and the dissolved copper diffuses through an insulating portion and
deposits on the copper circuit corresponding to a cathode, so that the
insulation between the circuits is broken. When the copper migration
happens at the interface between a resin and the glass fabric which is
located between the through-holes or between the through-hole and the
conductive pattern of the internal layer, it is called a CAF (Conductive
Anodic Filaments). It is believed that the CAF is caused by an
insufficient adhesion between the resin and the glass fabric. In other
words, it is believed that the CAF happens through a clearance between the
resin and glass fabric which is caused when the adhesion therebetween is
poor, or by damages of drilling of the through-holes. Therefore, it is
possible to prevent the occurrence of the CAF by improving the adhesion
between the resin and glass fabric.
Consequently, a more effective surface-treatment of the glass fabric is
desired to improve the above described problems.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a process for a
surface treatment of a glass fabric for improving the above problems. That
is, the process comprises the steps of exposing the glass fabric to an
atmospheric pressure plasma of a mixture gas including a reaction gas to
obtain a plasma-treated surface of the glass fabric, and coating an
organosilane compound on the plasma-treated surface of the glass fabric.
By exposing the glass fabric including an organic compound as a sizing
agent to the atmospheric pressure plasma, the organic compound can be
efficiently removed from the glass fabric. On the other hand, by exposing
a glass fabric, to which a heat-cleaning treatment is performed prior to
the exposing step of the present invention, to the atmospheric pressure
plasma, it is possible to remove a residue, e.g., carbon, of the sizing
agent left on the glass fabric after the heat-cleaning treatment. In
addition, the moisture or impurity adsorbed on the glass fabric after the
heat-cleaning treatment can be removed by the exposing step. Therefore,
the exposing step of the present invention is useful to improve adhesion
between the organosilane compound and the glass fabric and prevent the
occurrence of CAF (Conductive Anodic Filaments). Since the mixture gas is
pre-heated prior to a plasma excitation thereof, it is possible to
uniformly provide the above described effects of the exposing step to the
glass fabric.
It is preferred that the reaction gas is at least one of an oxidative gas
and a fluorine-containing gas. It is also preferred that the reaction gas
is one of a hydrogen-containing gas and a mixture gas of hydrogen gas and
the fluorine-containing gas. In particular, when the reaction gas contains
the fluorine-containing gas, the glass fabric is etched by the atmospheric
pressure plasma to form a finely-roughened surface on the glass fabric.
The roughened surface is useful to improve the adhesion between the
coupling agent and the glass fabric.
It is also preferred that the exposing step comprises the sub-steps of
exposing the glass fabric to a first atmospheric pressure plasma of a
first reaction gas containing the oxidative gas to obtain a pre-treated
surface of the glass fabric, and exposing the pre-treated surface to a
second atmospheric pressure plasma of a second reaction gas containing the
fluorine-containing gas to obtain the plasma-treated surface of the glass
fabric.
Other features, advantages and effects of the present invention will become
apparent by the detailed explanation below with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a plasma reaction apparatus used in the
present invention;
FIG. 2 is a schematic diagram helpful for understanding a method of
measuring an adhesion strength between a resin and a glass fabric; and
FIG. 3 is a plan view of a copper clad laminate prepared to estimate a
resistance to CAF (Conductive Anodic Filaments).
DETAILED DESCRIPTION OF THE INVENTION
A process for a surface treatment of a glass fabric of the present
invention is explained in detail. The process comprises the following
first and second steps. The first step is characterized by exposing the
glass fabric to an atmospheric pressure plasma of a mixture gas containing
a reaction gas to obtain a plasma-treated surface of the glass fabric. In
the first step, the mixture gas is pre-heated prior to the plasma
excitation thereof. The second step is characterized by coating an
organosilane compound on the plasma-treated surface of the glass fabric.
The pre-heating of the mixture gas is very important to uniformly and
efficiently perform the first step. That is, in case of performing a
plasma treatment to a substrate under a reduced pressure, since an amount
of thermal energy supplied from the plasma to the substrate is small, it
is generally required to heat the substrate to enhance the plasma
treatment. However, as a scale of the substrate is larger, it would be
more difficult to uniformly heat the substrate, in other words, uniformly
perform the plasma treatment to the substrate.
In case of performing a plasma treatment to the substrate under atmospheric
pressure, the thermal energy required to heat the substrate can be
supplied by a gas convection. The heat transfer by the gas convection can
not be attained under reduced pressure. Therefore, even when the substrate
is a relatively large scale, it is possible to uniformly perform the
plasma treatment to the substrate without using a heater or the like.
For example, a plasma reaction apparatus shown in FIG. 1 may be used for
the first step of the present invention. The apparatus comprises a
tube-like reaction chamber 1, a gas inlet 7 for supplying the mixture gas
into the reaction chamber 1, and a pair of upper and lower electrodes 2
and 3 for exciting the atmospheric pressure plasma 11 of the mixture gas.
The upper electrode 2 is disposed parallel to the lower electrode 3 and
spaced away from the lower electrode 3 by a predetermined distance. The
electrodes 2 and 3 are insulated from the reaction chamber 1. A
solid-dielectric 6 is placed on the lower electrode 3 between the
electrodes 2 and 3. The solid-dielectric 6 is useful to prevent the
occurrence of an arc discharge and to maintain a glow discharge during the
plasma excitation. It is possible to place the solid-dielectric on the
upper electrode, or solid-dielectrics both the electrodes, respectively.
The upper electrode 2 is connected to an alternating-current power source
5. It is preferred that the power source 5 can provide an
alternating-current power of a frequency of 50 Hz to 13.56 MHz. The lower
electrode 3 is connected to the earth. A thermocouple (not shown) is
inserted into the reaction chamber 1 to monitor a temperature of the
mixture gas in the atmospheric pressure plasma 11. Numeral 4 designates a
glass fabric arranged between the electrodes 2 and 3. It is preferred that
the glass fabric 4 is arranged between the electrodes so as to keep a
floated state thereof. The apparatus has a pair of feed and take-up reels
(not shown) used for continuously supplying a long sheet of the glass
fabric 4 into the reaction chamber 1, and a motor (not shown) for driving
those reels to transfer the long sheet at a predetermined feed speed in a
longitudinal direction of the reaction chamber 1, as shown by the arrow of
FIG. 1. Therefore, it is possible to continuously expose such a long sheet
of the glass fabric 4 to the atmospheric pressure plasma 11. A plasma
treatment time may be determined by the feed speed of the glass fabric.
For example, it is possible to complete the first step within about 20
min.
A carrier gas is supplied to the reaction chamber 1 from a carrier gas bomb
9 through the gas inlet 7. An alternating-current power is applied to the
electrodes 2 and 3 to generate a glow discharge of the carrier gas between
the electrodes. Subsequently, the reaction gas is supplied from a reaction
gas bomb 10 to the reaction chamber 1 through a gas mixing equipment 8 to
obtain the atmospheric pressure plasma 11 of the mixture gas. A flow rate
of the reaction gas is controlled to obtain a requested mixture ratio of
the reaction gas to the carrier gas. The mixture gas is pre-heated at a
requested temperature by a heater 12 prior to the supply to the reaction
chamber 1. It is preferred to supply the mixture gas so as to blow against
the glass fabric. It is also preferred that the mixture gas supplied to
the reaction chamber is forcedly stirred within the reaction chamber 1
with the use of a fan (not shown).
It is preferred that the mixture gas is pre-heated at a temperature between
100.degree. C. to 600.degree. C. prior to the plasma excitation. In this
case, it is confirmed that a residual carbon amount on the glass fabric is
considerably decreased by the first step, so that the adhesion between a
resin and the glass fabric can be improved. It is believed that when the
mixture gas is pre-heated at the temperature, radicals and ions in the
atmospheric pressure plasma attack strongly the glass fabric, so that a
reaction speed of the mixture gas to an organic compound as a sizing agent
or the residual carbon on the glass fabric is increased. It is also
believed that since a plasma cleaning is efficiently and uniformly
performed over the entire surface of the glass fabric, and a
finely-roughened surface is formed on the glass fabric during the first
step, the adhesion between the resin and the glass fabric can be improved.
When the mixture gas is pre-heated at a temperature less than 100.degree.
C., the plasma treatment time required to obtain the improved adhesion is
increased because the reaction speed is a relatively slow. When the
mixture gas is pre-heated at a temperature more than 600.degree. C., the
glass fiber would be softened.
It is preferred that at least one of an oxidative gas and a
fluorine-containing gas is used as the reaction gas. When a mixture of the
oxidative gas and fluorine-containing gas is used as the reaction gas, a
mixture ratio of the oxidative gas to the fluorine-containing gas may be
preferably selected from the range of 1/3 to 3/1.
It is also preferred that the glass fabric is exposed to a first
atmospheric pressure plasma of a first reaction gas containing the
oxidative gas, and then a second atmospheric pressure plasma of a second
reaction gas containing the fluorine-containing gas. In the first plasma,
the organic compound or carbon left on the glass fabric is converted in
the form of carbon dioxide, and removed from the glass fabric together
with the moisture and impurity adsorbed on the glass fabric. It is
preferred that the oxidative gas is at least one gas selected from the
group consisting of oxygen, air, and carbon dioxide. In the second plasma,
a surface of the glass fabric is etched, while the organic compound or
residual carbon is removed from the glass fabric together with the
moisture and impurity. That is, silicon oxide of the glass fabric is
etched by reacting with fluorine in the second reaction gas. The entire
surface of the glass fabric is finely and uniformly roughened by the
second plasma. The finely-roughened surface of the glass fabric is useful
to improve the adhesion between the resin and glass fabric.
It is also preferred that one of a hydrogen-containing gas and a mixture of
hydrogen gas and the fluorine-containing gas is used as the reaction gas.
In case of using the hydrogen-containing gas, the organic compound or the
residual carbon on the glass fabric is converted in the form of
hydrocarbon, and removed from the glass fabric together with the moisture
and impurity to obtain a cleaned and active surface of the glass fabric.
In particular, the addition of hydrogen gas to the fluorine-containing gas
enhances the plasma excitation of the fluorine-containing gas to improve a
reaction speed of the atmospheric pressure plasma to the glass fabric.
When a mixture of hydrogen gas and the fluorine-containing gas is used as
the reaction gas, a mixture ratio of the hydrogen gas to the
fluorine-containing gas may be preferably selected from the range of 1/3
to 3/1. It is preferred that the fluorine-containing gas is at least one
gas selected from the group consisting of hydrofluoride (HF), sulfur
hexafluoride (SF.sub.6), fluorine, nitrogen trifiuoride (NF.sub.3), carbon
tetrafluoride (CF.sub.4), trifiuoromethane (CHF.sub.3), and dicarbon
hexafluoride (C.sub.2 F.sub.6).
It is preferred that the mixture gas contains a rare gas such as argon
and/or helium as a carrier gas of the reaction gas. It is also preferred
that a concentration of the reaction gas in the mixture gas is 15 vol % or
less.
It is further preferred to perform the first step of the present invention
in place of a heat-cleaning treatment for removing the organic compound
from the glass fabric including the organic compound. In addition, it is
possible to perform the first step after the heat-cleaning treatment. That
is, the organic compound or the residual carbon left on the glass fabric
after the heat-cleaning treatment can be removed by the first step. Since
the finely-roughened surface can be formed on the glass fabric by the
first step, it is possible to provide an improved adhesion between the
glass fabric and the organosilane compound formed in the second step of
the present invention. Additionally, as shown in FIG. 1, since the first
step uses the atmospheric pressure plasma, it is easy to continuously
perform the first step to the glass fabric even when the glass fabric is
provided in the shape of a long sheet. As a result, the first step of the
present invention can provide an increased production rate of the glass
fabric having the plasma-treated surface with the use of a relatively
inexpensive and simple plasma-reaction apparatus.
In the second step of the present invention, the organosilane compound is
coated on the plasma-treated surface of the glass fabric to improve the
wettability of the resin to the glass fabric. The organosilane compound is
known as a coupling agent. For example, a solution including the coupling
agent is impregnated into the glass fabric by means of dipping or
spraying, and then dried. The solution substantially consists of the
organosilane compound and a solvent such as alcohol or water. It is
preferred that a concentration of the organosilane compound in the
solution is in the range 0.1 to 2 wt %. The organosilane compound
comprises vinylmethoxy-silane, vinylphenyltrimethoxy-silane,
3-methacryloxypropyltrimethoxy-silane, 3-glycidoxypropyltrimethoxy-silane,
3-aminopropyltriethoxy-silane, 4-glycidylbutyltrimethoxy-silane,
N-2-(aminoethyl)-3-aminopropyltrimethoxy-silane,
N-2-(N-vinylbenzylaminoethyl) -3-aminopropyltrimethoxyo-silane
hydrochloride,
N-3-(4-(3-aminopropoxy)butoxy)propyl-3-aminopropyltrimethoxy-silane,
3-mercaptopropyltrimethoxy-silane, imidazole-silane, or the like.
It is preferred that the organosilane compound is coated on the
plasma-treated surface of the glass fabric by a plasma polymerization
method. A mixture gas of a vaporized gas of an organosilane monomer and a
rare gas as a carrier gas, e.g., argon and/or helium, can be used for the
plasma polymerization method. The plasma-treated surface of the glass
fabric is exposed to an atmospheric pressure plasma of the mixture gas to
coat the organosilane compound thereon. In addition to the above listed
organosilane compounds, the organosilane monomer comprises
tetramethoxy-silane, trimethoxy-silane, triethoxy-silane,
vinyltriethoxy-silane, hexamethyl-disilane, tetraethoxy-silane,
hexamethyl-disiloxane, or the like. When the plasma reaction apparatus of
FIG. 1 is modified to supply the vaporized organosilane gas together with
the carrier gas into the reaction chamber, it is possible to basically use
the modified apparatus to perform the plasma polymerization method. It is
preferred that a small amount of oxygen is added to the mixture gas to
enhance the coating of the organosilane compound. It is also preferred
that a temperature of the mixture gas of the vaporized gas and rare gas in
the plasma zone is in the range of 100.degree. C. and 500.degree. C. to
improve the adhesion between the glass fabric and the organosilane
compound and prevent the occurrence of the CAF.
The glass fabric used in the present process comprises a glass fabric
including a large amount of the organic compound as the sizing agent
without the heat-cleaning treatment, and a glass fabric including a small
amount, e.g., 0.1% or less, of the organic compound or the residual
carbon, to which the heat-cleaning treatment is performed prior to the
first step of the present invention. The organic compound comprises a
starch, polyvinyl alcohol, or the like. In particular, when the first step
is performed to the later glass fabric, the residual carbon can be almost
completely removed from the glass fabric, and the formation of a
finely-roughened surface of the glass fabric is enhanced.
EXAMPLES 1 TO 8
Glass yarns (Japanese Industrial Standard (JIS): E type) were woven while
applying an organic compound as a sizing agent thereto, so that glass
fabrics including the organic compound were obtained. The glass fabric
corresponds to a glass cloth of JIS 3414-EP18. Subsequently, surface
treatments of the present invention were performed to the glass fabrics in
accordance with process conditions shown on TABLES 1 and 2 to obtain
products of EXAMPLES 1 to 8.
For example, the product of EXAMPLE 1 was prepared as follows. In a first
plasma treatment, the glass fabric was exposed to a first atmospheric
pressure plasma of a first mixture gas of oxygen as a first reaction gas
and helium as a carrier gas. Flow rates of the first reaction gas and
carrier gas are 0.04 L(liter)/min and 1.96 L(liter)/min, respectively. An
alternating current power source of the frequency of 13. 56 MHz was used
for the plasma excitation of the first plasma. The first mixture gas was
pre-heated at the temperature of 150.degree. C. by a heater prior to the
plasma excitation. The glass fabric was kept in the first plasma for 5 min
to obtain a cleaned surface of the glass fabric.
In a second plasma treatment, the cleaned surface of the glass fabric was
exposed to a second atmospheric pressure plasma of a second mixture gas of
carbon tetrafluoride (CF.sub.4) as a second reaction gas and helium as a
carrier gas. Flow rates of the second reaction gas and carrier gas are
0.06 L/min and 1.94 L/min, respectively. The alternating current power
source of the frequency of 13.56 MHz was used for the plasma excitation of
the second plasma. The second mixture gas was not heated prior to the
plasma excitation. The glass fabric was kept in the second plasma for 5
min to obtain a plasma-treated surface of the glass fabric.
In a third plasma treatment, the plasma-treated surface of the glass fabric
was exposed to a third atmospheric pressure plasma of a third mixture gas
of 3-aminopropyltriethoxy-silane gas as an organosilane gas and helium as
a carrier to coat an organosilane compound on the plasma-treated surface.
The organosilane gas was prepared by vaporizing an organosilane monomer. A
supply rate of the organosilane gas is 50 mg/min. The supply rate was
measured by a mass spectrometer. A flow rate of the carrier gas is 2.0
L/min. An alternating current power source of the frequency of 13.56 MHz
was used for the plasma excitation of the third plasma. The third mixture
gas was not heated prior to the plasma excitation. The glass fabric was
kept in the third plasma for 5 min to obtain the product of EXAMPLE 1.
In each of EXAMPLES 4, 5 and 8, a dip treatment was performed after the
second plasma treatment in place of the third plasma treatment. For
example, in EXAMPLE 4, the dip treatment was performed by impregnating an
aqueous solution of 3-aminopropyltriethoxy-silane into the glass fabric.
The concentration of 3-aminopropyltriethoxy-silane in the aqueous solution
is 2%. After the dip treatment, the glass fabric was dried at the
temperature of 150.degree. C. for 60 minutes to obtain the product of
EXAMPLE 4.
EXAMPLES 9 TO 19
Glass yarns (Japanese Industrial Standard (JIS): E type) were woven while
applying an organic compound as a sizing agent thereto, so that glass
fabrics including the organic compound were obtained. The glass fabric
corresponds to a glass cloth of JIS 3414-EP18. A heat-cleaning treatment
was performed to the glass fabrics at the temperature of 400.degree. C.
for 48 hours to remove the organic compound from the glass fabrics. After
the heat-cleaning treatment, it was confirmed that 0.08% of carbon was
left on the glass fabric as a residual carbon. Subsequently, surface
treatments of the present invention were performed to the glass fabrics in
accordance with process conditions shown on TABLES 3 to 5 to obtain
products of EXAMPLES 9 to 19.
For example, the product of EXAMPLE 13 was prepared as follows. In a first
plasma treatment, the glass fabric was exposed to a first atmospheric
pressure plasma of a first mixture gas of sulfur hexafluoride (SF.sub.6)
and hydrogen as first reaction gases and helium and argon as carrier
gases. Flow rates of sulfur hexafluoride (SF.sub.6) and hydrogen are 0.05
L/min, respectively. Flow rates of helium and argon are 1.00 L/min and
0.90 L/min, respectively. An alternating current power source of the
frequency of 2 MHz was used for the plasma excitation of the first plasma.
The first mixture gas was pre-heated at the temperature of 350.degree. C.
by a heater prior to the plasma excitation. The glass fabric was kept in
the first plasma for 5 min to obtain a plasma-treated surface of the glass
fabric.
In a second plasma treatment, the plasma-treated surface of the glass
fabric was exposed to a second atmospheric pressure plasma of a second
mixture gas of hexamethyl-disiloxane gas as an organosilane gas and helium
as a carrier to coat an organosilane compound on the plasma-treated
surface. The organosilane gas was prepared by vaporizing an organosilane
monomer. A supply rate of the organosilane gas is 20 mg/min. The supply
rate was measured by a mass spectrometer. A flow rate of the carrier gas
is 2.0 L/min. An alternating current power source of the frequency of 15
KHz was used for the plasma excitation of the second plasma. The second
mixture gas was pre-heated at the temperature of 200.degree. C. prior to
the plasma excitation. The glass fabric was kept in the second plasma for
10 min to obtain the product of EXAMPLE 13.
In each of EXAMPLES 10, 15, 16, and 18, a dip treatment was performed after
the first plasma treatment in place of the second plasma treatment. For
example, in EXAMPLE 16, the dip treatment was performed by impregnating an
ethanol solution of 3-glycidoxypropyltrimethoxy-silane into the glass
fabric. The concentration of 3-glycidoxypropyltrimethoxy-silane in the
ethanol solution is 2%. After the dip treatment, the glass fabric was
dried at the temperature of 100.degree. C. for 60 minutes to obtain the
product of EXAMPLE 16.
COMPARATIVE EXAMPLE 1
A glass fabric including an organic compound, which is the same as that
used in EXAMPLE 1, was used in COMPARATIVE EXAMPLE 1. A heat-cleaning
treatment was performed in an electric furnace at the temperature of
400.degree. C. for 48 hours to remove the organic compound from the glass
fabric. Then, the glass fabric was dipped into an aqueous solution of
3-aminopropyltriethoxy-silane for 1 minute, and then dried at the
temperature of 150.degree. C. for 60 minutes to obtain a product of
COMPARATIVE EXAMPLE 1. The concentration of 3-aminopropyltriethoxy-silane
in the aqueous solution is 2 wt %.
COMPARATIVE EXAMPLE 2
A product of COMPARATIVE EXAMPLE 2 was prepared in accordance with the same
process of EXAMPLE 1 except that the first mixture gas was not heated
prior to the plasma excitation of the first plasma. In this case, it was
confirmed that a temperature of the first mixture gas in a plasma zone of
the first plasma is in the range of a room temperature to 70.degree. C.
COMPARATIVE EXAMPLE 3
A product of COMPARATIVE EXAMPLE 3 was prepared in o accordance with the
same process of EXAMPLE 4 except that the second mixture gas was not
heated prior to the plasma excitation of the second plasma. In this case,
it was confirmed that a temperature of the second mixture gas in a plasma
zone of the second plasma is in the range of a room temperature to
70.degree. C.
COMPARATIVE EXAMPLE 4
A product of COMPARATIVE EXAMPLE 4 was prepared in accordance with the same
process of EXAMPLE 5 except that the second mixture gas was not heated
prior to the plasma excitation of the second plasma. In this case, it was
confirmed that a temperature of the second mixture gas in a plasma zone of
the second plasma is in the range of a room temperature to 70.degree. C.
COMPARATIVE EXAMPLE 5
A product of COMPARATIVE EXAMPLE 5 was prepared in accordance with the same
process of EXAMPLE 6 except that the first mixture gas was not heated
prior to the plasma excitation of the first plasma. In this case, it was
confirmed that a temperature of the first mixture gas in a plasma zone of
the first plasma is in the range of a room temperature to 70.degree. C.
COMPARATIVE EXAMPLE 6
A product of COMPARATIVE EXAMPLE 6 was prepared in accordance with the same
process of EXAMPLE 7 except that the second mixture gas was not heated
prior to the plasma excitation of the second plasma. In this case, it was
confirmed that a temperature of the second mixture gas in a plasma zone of
the second plasma is in the range of a room temperature to 70.degree. C.
COMPARATIVE EXAMPLE 7
A product of COMPARATIVE EXAMPLE 7 was prepared in accordance with the same
process of EXAMPLE 8 except that the second mixture gas was not heated
prior to the plasma excitation of the second plasma. In this case, it was
confirmed that a temperature of the second mixture gas in a plasma zone of
the second plasma is in the range of a room temperature to 70.degree. C.
The following experiments 1-3 were performed with respect to the products
of EXAMPLES 1-19 and COMPARATIVE EXAMPLES 1-7.
[1] EXPERIMENT 1
A residual carbon amount left on the glass fabric immediately before the
coating of the organosilane compound was measured by the use of a carbon
mass spectrometer. Results are listed on TABLE 6.
[2] EXPERIMENT 2
For estimating an adhesion strength between a resin and each of the
products of EXAMPLES 1-19 and COMPARATIVE EXAMPLES 1-7, a copper clad
laminate was manufactured, and an adhesion strength between prepregs of
the copper clad laminate was measured as follows. An epoxy resin varnish
was prepared by dissolving a brominated bisphenol-A type epoxy resin,
dicyandiamide as a curing agent and 2- ethyl-4-methyl-imidazole as a
catalyst into methylcellosolve as a solvent. The varnish was impregnated
into each of the products, and then dried at the temperature of
150.degree. C. for 8 min to obtain the prepreg. A resin content in the
prepreg is in the range of 43 to 46 wt %. A melting viscosity of the epoxy
resin in the prepreg is in a range of 400 to 700 poises at 130.degree. C.
It took 120 to 160 seconds as a required time for gelation at 170.degree.
C. After four prepregs were stacked to obtain a prepreg assembly, the
assembly was sandwiched between a pair of copper foils of 18 .mu.m thick.
The prepreg assembly having the copper foils was compressed under 40
kg/cm.sup.2 at 170.degree. C. for 90 minutes to obtain the copper clad
laminate. As shown in FIG. 2, when an upper prepreg 33 with a top copper
foil 34 of the clad laminate 30 was separated from lower prepregs 32 with
a bottom copper foil 31 of the clad laminate 30 by a vertical force, the
adhesion strength between the prepregs was determined in accordance with
the vertical force. Results are listed on TABLE 6.
[3] EXPERIMENT 3
A resistance to CAF (Conductive Anodic Filaments) of a prepreg was
estimated as follows. Eight prepregs, each of which is the same as that
used in the experiment 2, were stacked to obtain a prepreg assembly. The
prepreg assembly was sandwiched between a pair of copper foils of 18 .mu.m
thick. The prepreg assembly having the copper foils was compressed under
40 kg/cm.sup.2 at 170.degree. C. for 90 minutes to obtain a copper clad
laminate 40 having the thickness of 1.6 mm. As shown in FIG. 3, four
hundreds through-holes 41 having the diameter of 0.9 mm were drilled in
the clad laminate 40. Subsequently, top and bottom circuit patterns were
formed on the clad laminate. In FIG. 3, solid lines connecting to
through-holes 41 designates the top circuit patterns, and dotted lines
connecting to the though-holes 41 designates the bottom circuit patterns.
A copper plating was performed to the through-holes 41 to connect the top
circuit patterns with the bottom circuit patterns. When a direct-current
voltage of 35 V was applied between electrodes 42 and 43 on the clad
laminate 40 under an atmosphere with the temperature of 85.degree. C. and
the relative humidity of 85%, a time period necessary for causing a
short-circuit was measured as a value indicative of the resistance to CAF.
Therefore, as the time period necessary for causing the short-circuit is
extended, it would be understood that the resistance to CAF is more
improved. Results are listed on TABLE 6.
Each of the residual carbon contents of the glass fabrics of EXAMPLES 1-9
is equal to or less than that of the glass fabric of COMPARATIVE EXAMPLE
1. Therefore, the organic compound can be efficiently removed from the
glass fabric by performing the plasma treatment of the present invention
for several minutes in place of performing the heat-cleaning treatment of
the prior art for several ten hours. When the results of the experiments
1-3 with respect to EXAMPLES 1 and 4-8 are compared with those with
respect to COMPARATIVE EXAMPLES 2-7, it would be understood that the
preheating of the first mixture gas and/or second mixture gas prior to the
plasma excitation is useful to provide more improved adhesion strength and
resistance to CAF to the clad laminates. In addition, as evidenced by
EXAMPLES 9-19, it is preferred to perform the surface treatment of the
present invention after the heat-cleaning treatment to obtain good copper
clad laminates.
TABLE 1
__________________________________________________________________________
EXAMPLE 1
EXAMPLE 2
EXAMPLE 3
EXAMPLE 4
__________________________________________________________________________
First Plasma:
Output Power:
500 W 500 W 500 W 700 W
Frequency:
13.56 MHz
13.56 MHz
13.56 MHz
5.0 MHz
Gas Temperature:
150.degree. C.
No-heat 150.degree. C.
No-heat
Treatment Time:
5 min 5 min 5 min 10 min
Carrier Gas:
He He He He
Flow Rate:
1.96 L/min
1.96 L/min
1.96 L/min
1.90 L/min
Reaction Gas:
O.sub.2
O.sub.2 O.sub.2
O.sub.2
Flow Rate:
0.04 L/min
0.04 L/min
0.04 L/min
0.10 L/min
Second Plasma:
Output Power:
500 W 500 W 500 W 700 W
Frequency:
13.56 MHz
13.56 MHz
13.56 MHz
5.0 MHz
Gas Temperature:
No-heat
150.degree. C.
150.degree. C.
250.degree. C.
Treatment Time:
5 min 5 min 5 min 10 min
Carrier Gas:
He He He He
Flow Rate:
1.94 L/min
1.94 L/min
1.94 L/min
1.94 L/min
Reaction Gas:
CF.sub.4
CF.sub.4
CF.sub.4
CF.sub.4
Flow Rate:
0.06 L/min
0.06 L/min
0.06 L/min
0.06 L/min
Third Plasma: Not
Output Power:
500 W 500 W 500 W performed
Frequency:
13.56 MHz
13.56 MHz
13.56 MHz
Gas Temperature:
No-heat
No-heat 150.degree. C.
Treatment Time:
5 min 5 min 5 min
Carrier Gas:
He He He
Flow Rate:
2.0 L/min
2.0 L/min
2.0 L/min
Organosilane Gas:
3-amino-
3-amino-
3-amino-
propyl-
propyl- propyl-
triethoxy-
triethoxy-
triethoxy-
silane silane silane
Supply Rate:
50 mg/min
50 mg/min
50 mg/min
Dip Treatment:
Not Not performed
Not
Organosilane:
performed performed
3-amino-
propyl-
triethoxy-
silane
Concentration: 2%
Solvent: Water
Temperature: 150.degree. C.
Drying Time: 60 min
__________________________________________________________________________
TABLE 2
__________________________________________________________________________
EXAMPLE 5
EXAMPLE 6
EXAMPLE 7
EXAMPLE 8
__________________________________________________________________________
First Plasma:
Not Not Not performed
Output Power:
performed
500 W performed
Frequency: 2.0 MHz
Gas Temperature:
300.degree. C.
Treatment Time: 10 min
Carrier Gas: He + Ar
Flow Rate: He: 1.5 L/min
Ar: 0.4 L/min
Reaction Gas: Air
Flow Rate: 0.10 L/min
Second Plasma: Not performed
Output Power:
400 W 500 W 400 W
Frequency:
10.0 MHz 5.0 MHz
10.0 MHz
Gas Temperature:
250.degree. C. 300.degree. C.
300.degree. C.
Treatment Time:
10 min 20 min 10 min
Carrier Gas:
He He He
Flow Rate:
1.90 L/min 1.90 L/min
1.90 L/min
Reaction Gas:
C.sub.2 F.sub.6
CF.sub.4
CF.sub.4 + O.sub.2
Flow Rate:
0.10 L/min 0.10 L/min
CF.sub.4 :
0.05 L/min
O.sub.2 : 0.05 L/min
Third Plasma:
Not Not performed
Output Power:
performed
200 W 200 W
Frequency: 10.0 MHz
15 KHz
Gas Temperature:
200.degree. C.
No-heat
Treatment Time: 10 min 10 min
Carrier Gas: He + O.sub.2
He
Flow Rate: He: 1.95 L/min
2.0 L/min
O.sub.2 : 0.05 L/min
Organosilane Gas:
Tetraethoxy-
Hexamethyl-
silane disiloxane
Supply Rate: 10 mg/min
20 mg/min
Dip Treatment: Not performed
Not
Organosilane:
3-glycidoxy- performed
3-amino-
propyl- propyl-
trimethoxy- triethoxy-
silane silane
Concentration:
2% 1%
Solvent: Ethanol Ethanol
Temperature:
100.degree. C. 150.degree. C.
Drying Time:
60 min 60 min
__________________________________________________________________________
TABLE 3
__________________________________________________________________________
EXAMPLE 9
EXAMPLE 10
EXAMPLE 11
EXAMPLE 12
__________________________________________________________________________
First Plasma:
Output Power:
500 W 700 W 700 W 500 W
Frequency:
13.56 MHz
5 MHz 10 MHz 500 KHz
Gas Temperature:
150.degree. C.
200.degree. C.
250.degree. C.
300.degree. C.
Treatment Time:
5 min 10 min 5 min 5 min
Carrier Gas:
He He Ar He
Flow Rate:
1.94 L/min
1.94 L/min
1.90 L/min
1.90 L/min
Reaction Gas:
CF.sub.4
C.sub.2 F.sub.6
O.sub.2 + CF.sub.4
O.sub.2
Flow Rate:
0.06 L/min
0.06 L/min
O.sub.2 : 0.05 L/min
0.10 L/min
CF.sub.4 : 0.05 L/min
Second Plasma: Not performed
Output Power:
500 W 500 W 500 W
Frequency:
13.56 MHz 13.56 MHz
13.56 MHz
Gas Temperature:
50.degree. C. 150.degree. C.
150.degree. C.
Treatment Time:
5 min 5 min 5 min
Carrier Gas:
He He He
Flow Rate:
2.0 L/min 2.0 L/min
2.0 L/min
Organosilane Gas:
3-amino- 3-amino- Tetraethoxy-
propyl- propyl- silane
triethoxy- triethoxy-
silane silane
Supply Rate:
50 mg/min 50 mg/min
50 mg/min
Dip Treatment:
Not Not performed
Not
Organosilane:
performed
3-amino- performed
propyl-
triethoxy-
silane
Concentration: 2%
Solvent: Water
Temperature: 150.degree. C.
Drying Time: 60 min
__________________________________________________________________________
TABLE 4
__________________________________________________________________________
EXAMPLE 13
EXAMPLE 14
EXAMPLE 15
EXAMPLE 16
__________________________________________________________________________
First Plasma:
Output Power:
500 W 1000 W 700 W 400 W
Frequency:
2 MHz 500 KHz 5.0 MHz 10.0 MHz
Gas Temperature:
350.degree. C.
200.degree. C.
250.degree. C.
250.degree. C.
Treatment Time:
5 min 10 min 10 min 10 min
Carrier Gas:
He + Ar Ar Ar He
Flow Rate:
He: 1.0 L/min
1.94 L/min
1.94 L/min
1.90 L/min
Ar: 0.90 L/min
Reaction Gas:
SF.sub.6 + H.sub.2
HF H.sub.2 C.sub.2 F.sub.6 + H.sub.2
Flow Rate:
SF.sub.6 :
0.06 L/min
0.06 L/min
C.sub.2 F.sub.6 :
0.05 L/min 0.05 L/min
H.sub.2 : 0.05 H.sub.2 : 0.05
L/min
Second Plasma: Not Not
Output Power:
200 W 500 W performed
performed
Frequency:
15 KHz 500 KHz
Gas Temperature:
200.degree. C.
150.degree. C.
Treatment Time:
10 min 10 min
Carrier Gas:
He He
Flow Rate:
2.0 L/min
2.0 L/min
Organosilane Gas:
Hexamethyl-
3-amino-
disiloxane
propyl-
triethoxy-
silane
Supply Rate:
20 mg/min
50 mg/min
Dip Treatment:
Not performed
Not performed
Organosilane: 3-amino-
3-glycidoxy-
propyl- propyl-
triethoxy-
trimethoxy-
silane silane
Concentration: 2% 2%
Solvent: Water Ethanol
Temperature: 150.degree. C.
100.degree. C.
Drying Time: 60 min 60 min
__________________________________________________________________________
TABLE 5
______________________________________
EXAMPLE EXAMPLE
17 18 EXAMPLE 19
______________________________________
First Plasma:
Output Power:
500 W 500 W 500 W
Frequency: 100 KHz 13.56 MHz 10.0 MHz
Gas Temperature:
300.degree. C.
50.degree. C.
50.degree. C.
Treatment Time:
15 min 5 min 10 min
Carrier Gas:
He He He
Flow Rate: 1.90 L/min 1.94 L/min 1.90 L/min
Reaction Gas:
CF.sub.4 CF.sub.4 CF.sub.4 + O.sub.2
Flow Rate: 0.1 L/min 0.06 L/min CF.sub.4 : 0.05
L/min
O.sub.2 : 0.05
L/min
Second Plasma: Not
Output Power:
200 W performed 500 W
Frequency: 15 KHz 13.56 MHz
Gas Temperature:
150.degree. C. 50.degree. C.
Treatment Time:
10 min 5 min
Carrier Gas:
He He
Flow Rate: 2.0 L/min 2.0 L/min
Organosilane Gas:
Hexamethyl- 3-amino-propyl-
disiloxane triethoxy-silane
Supply Rate:
20 mg/min 50 mg/min
Dip Treatment:
Not Not performed
Organosilane:
performed 4-glycidyl-
butyl-
trimethoxy-
silane
Concentration: 1%
Solvent: Ethanol
Temperature: 100.degree. C.
Drying Time: 60 min
______________________________________
TABLE 6
______________________________________
Residual Adhesion Resistance
carbon Strength to CAF
Content (%)
(kg/cm) (hours)
______________________________________
EXAMPLE 1 0.06 2.3 2400
EXAMPLE 2 0.06 2.5 2550
EXAMPLE 3 0.06 2.6 2650
EXAMPLE 4 0.08 2.5 2550
EXAMPLE 5 0.06 2.6 2500
EXAMPLE 6 0.06 2.3 2400
EXAMPLE 7 0.06 2.5 2600
EXAMPLE 8 0.06 2.5 2600
EXAMPLE 9 0.03 2.5 2500
EXAMPLE 10 0.03 2.7 2750
EXAMPLE 11 0.02 2.6 2700
EXAMPLE 12 0.04 2.5 2600
EXAMPLE 13 0.02 2.7 2650
EXAMPLE 14 0.02 2.6 2550
EXAMPLE 15 0.04 2.4 2500
EXAMPLE 16 0.03 2.8 2800
EXAMPLE 17 0.03 2.7 2600
EXAMPLE 18 0.05 2.5 2500
EXAMPLE 19 0.06 2.4 2450
COMPARATIVE 0.08 1.5 1500
EXAMPLE 1
COMPARATIVE 0.08 2.1 2100
EXAMPLE 2
COMPARATIVE 0.08 1.9 2000
EXAMPLE 3
COMPARATIVE 0.08 2.0 2100
EXAMPLE 4
COMPARATIVE 0.07 1.8 1950
EXAMPLE 5
COMPARATIVE 0.08 2.0 2050
EXAMPLE 6
COMPARATIVE 0.08 2.0 2000
EXAMPLE 7
______________________________________
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